Throughout the present document the term User Equipment (UE) is used. The term UE refers to any type of mobile terminal, such as a mobile telephone, personal digital assistance (PDA), etc, and the terms UE and mobile terminal are interchangeable.
Known wireless networks can comprise an “Access Network Discovery and Selection Function” (ANDSF), which is described for example in chapter 4.8 of 3GPP specification 3GPP TS 23.402 V9.4.0 (March 2010), “Architecture enhancements for non-3GPP accesses”.
The packet core network and system referred to therein (“Evolved Packet Core Network” EPC, “Evolved 3GPP PS Domain”, EPS) allows a UE to be provided, via the ANDSF, with policies for selecting access networks through which to connect to the packet core network (EPC).
The information provided by the ANDSF allows the UE to scan for access networks and to decide which access network to select among a plurality of access networks, based on data and policies.
Detailed background information of the current state of the art with respect to the ANDSF, and its interaction with UE(s), is provided below.
The ANDSF is a network element that contains data management and control functionality necessary to provide network discovery and selection assistance data in accordance with the operator(s) policy.
The introduction of ANDSF does not impact on the attach procedures for any of the accesses. In particular, it does not interfere with the existing 3GPP PLMN selection mechanisms used for the 3GPP Access Technologies.
ANDSF defines a simple client-server architecture with single Access Network Info Request and Response messages. UEs may contact the ANDSF server by sending an Access Network Info Request message to it. The ANDSF server responds to the UE by sending an Access Network Info Response message. The ANDSF is specified in 3GPP TS 23.402, “Architecture enhancements for non-3GPP accesses”, and 3GPP TS 24.302, “Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks”.
In Access Network Info Response messages, the ANDSF provides two types of information: an inter-system mobility policy and access network discovery information.
With an inter-system mobility policy, an operator, or any other organization maintaining an ANDSF server, can affect which networks UEs are using.
For example, an inter-system mobility policy may contain a prioritized network list that advises the UE about a priority order an which it can consider access networks during the access network selection process. The inter-system mobility policies received from the ANDSF take precedence over those statically provisioned in the UE.
The UE can be configured in automatic or manual mode. In automatic mode, the UE may, at its discretion, accept policies and execute changes of access networks according to the received policies. In manual mode, the consent of the user is required prior to accepting a policy and executing it.
In the above known system, policies sent by the ANDSF are merely advice for selecting by the UE an access network, for example in case of roaming or handover.
Access network discovery information is intended to help the UE to discover networks in its neighbourhood. For example, the access network discovery information may contain information on the network type, network ID, used radio frequency and channel. With this information, the UE may perform a network scan (i.e. discovery) more efficiently, since it does not need to go through all the possible access network technologies and frequency bands. By nature, the access network discovery information may be tied to a specific location and is also more short-lived than network selection information.
The ANDSF implements the S14 interface towards the User Equipment (UE). The interface is used to provide information on access networks available in the vicinity of the UE and information on operator's preference on these access networks. The S14 interface is implemented with OMA Device Management V1.2, OMA-ERELD-DM-V1—2—1, WAP Push OMA Push Architecture V2.3, OMA-AD-Push-V2—3-20091013-C, and a security mechanism that includes OMA DM bootstrap, secure HTTPS, IETF RFC 2616: Hypertext Transfer Protocol-HTTP/1.1, or GAA bootstrap, 3GPP TS 33.919: Generic Authentication Architecture (GAA); System description.
The information provided by the ANDSF is structured in a so-called OMA DM Managed Object, MO, according to what is specified in 3GPP TS 24.312, “Access Network Discovery and Selection Function (ANDSF) Management Object (MO).
The UE and ANDSF 814 interface supports both a pull and a push mode. In pull mode the UE initiates the communication to retrieve the data. In push mode the ANDSF initiates the communication to send data to the UE.
In order for the UE to receive information from the ANDSF, the UE has to have IP connectivity and to have discovered the ANDSF. If the ANDSF needs to push data and the UE does not have IP connectivity, or has not discovered the ANDSF, the ANDSF can use WAP push to force the UE to trigger the process.
The ANDSF can be located in the home network (H-ANDSF 1002) or in a visited network (V-ANDSF 1003), as shown in FIG. 1. For a UE 1001 that is roaming, it is possible that the UE 1001 acquires data from both the H-ANDSF 1002 and V-ANDSF 1003. In any case, the H-ANDSF 1002 and V-ANDSF 1003 do not have an interface between them. The interface specified between the UE 1001 and any of the H-ANDSF 1002 or V-ANDSF 1001 is the S14 interface.
The UE 1001 can also be statically provisioned with intersystem mobility policy and access network discovery information. In case the UE 1001 also acquires the same type of information from the network, the information acquired from the ANDSF has precedence over statically provisioned information in the UE 1001.
FIG. 2 shows a general information flow demonstrating signalling for both push and pull operation modes. The ANDSF 2002, at any time, can decide to push policy rules and discovery information to the UE 1001, using, for instance, WAP Push, as in step 901. The next steps are common for both push and pull modes. In step 902, the UE 1001 attaches its location information and requests the ANDSF 2002 to send the policy rules and discovery information. In step 903, the ANDSF 2002 filters the policy rules and discovery information according to the current location of the UE 1001 and then sends this filtered policy rules and discovery information to the UE 1001. Then the UE 1001 may need to switch new interfaces on or off, to try to attach to a new network (step 904), according to the information received from the ANDSF 2002. Eventually, the UE 1001 will attach to the new access network (step 905).
ANDSF 2002 is the node that manages two types of information: intersystem mobility policy and access network discovery information. Additionally, the UE 1001 is able to send to the ANDSF 2002 its UE current location.
An intersystem mobility policy is a set of operator-defined rules and preferences that affect the intersystem mobility decisions taken by the UE 1001. Therefore, intersystem mobility policies provide the UE 1001 with the means to prioritize the access network used by the UE 1001.
The access network discovery information merely provides the UE 1001 with additional information that helps the UE 1001 to gain access to the access network defined in the policy.
The ANDSF 2002 merely provisions the UE 1001 over the S14 interface with information policies for selecting access networks, wherein the final decision relies on information configured in the UE, and/or in decisions made by the UE's user.
The ANDSF MO contains three big chunks of data:                Inter-system Mobility Policy Rules: Composed of several conditions, including access network types (e.g. 3GPP, 3GPP2, WLAN, WiMAX), access network identifiers (e.g. PLMN, TAC. RAC, BSSID, etc), validity areas and time frames, among others, and a priority. The highest priority matched rule determines the access to be selected by the UE 1001.        Discovery Information: The discovery information data provides the UE 1001 with suitable data for helping in the discovery of access networks. This data contains the type of access network for which discovery information is provided (e.g., 3GPP, 3GPP2, WLAN, WiMAX); the access network area (e.g. PLMN, TAC, NAP-ID, BSSID, etc); and additional information on the specific access network.        UE location: The UE current location provides a placeholder for the UE 1001 to provide its current location to the ANDSF 2002, in terms of access network parameters or geographical location. This is used to filter the irrelevant data for the current location of the UE 1001.        
Consider a scenario where a core network 3005 is connected to two or more access networks, as depicted in FIG. 3. Access networks are available to the UE 1001, although it is not necessary that each access network provides access to the UE 1001 simultaneously at a given instance of time.
Assume that a UE 1001 is moving along a path, where a path is a successive series of positions relative to the location of a mobile user equipment.
For example, the UE 1001 may be located in a car that is moving at a certain speed in a highway or the UE 1001 may be located in a train that is moving over railway tracks, as shown in FIG. 4.
A problem addressed by embodiments of the present invention is now described with the help of FIG. 5.
A user and his UE 1001 are located in a moving car. The UE 1001 is able to connect to a number of access networks of the same or different types (e.g. 3GPP, WiMAX, WLAN, etc) installed along the path in a tunnel that the car can traverse (a similar example could be access networks available in a train where a user and his UE travel, which can be alternative to the current access network to which the UE currently attaches). In the example, the UE 1001 is assumed to be attached to the operator's core network 3005 via Access Network 1, which is one of the many possible access networks that the user can use to connect to the operator's core network. Some of these access networks can be preferred, under the UE's Home operator point of view, over others due to, for example, cost effectiveness, special agreements with the corresponding Visited operator, etc. In this context, the ANDS' 2002 can provide the UE 1001 with policies for selecting among these access networks.
In the considered scenario, the car is travelling along a highway. The highway comprises a trajectory that traverses a tunnel, for which the current access network that the UE 1001 is connected to, Access Network 1, does not offer coverage.
Now assume that a second access network, Access Network 2, offers coverage in the tunnel in which Access Network 1 does not provide coverage.
When known systems encounter the above-described scenario, the UE 1001 enters the tunnel, detects the lack of Access Network 1, switches on at least one additional interface corresponding to Access Network 2, samples that interface until a beacon is received, and tries to connect or attach to the home network via Access Network 2.
These processes of take time, typically ranging from a few seconds to several minutes. During the period of time from the loss of connectivity to Access Network 1 to the moment connectivity is established with Access Network 2, the UE 1001 is not able to get communication services and to be engaged in communications of any kind. Furthermore, the time before communication to the UE 1001 is re-established will increase if, for example, Access Network 2 denies access to the user of the UE 1001, and the UE 1001 has to repeat the operation with any of the remaining access networks.
Moreover, with regard to already established communications, if the UE 1001 moves at high speeds, for example if the user is travelling in a high-speed train or on a fast road, handover mechanisms can fail because the UE 1001 moves away from the cell to which the handover is being attempted before the handover process itself is completed.
The problem has been described by way of examples. However, it will be appreciated that the same problem occurs with many different types of area where the access network the UE 1001 is currently attached to cannot, or should preferably not, keep on providing services (for example, roaming services allowing said UE to register and initiate/receive incoming communications, or handover services allowing said UE 1001 to maintain ongoing communications).
For example, reasons for an access network not being able to keep on providing a service in a geographical area include:    1. The access network does not have coverage in that area.    2. The access network is congested, or suffering a malfunction, in that area.    3. The access network in the area is preferably reserved for a certain time for the usage of certain users. For example, it might be desirable to exclusively reserve access to a certain access network to UEs related to emergency or security services in an area where a disaster has occurred, in an area where an special event takes place, etc.    4. The UE 1001 is moving so fast that handover procedures with respect to the concerned access networks are likely not to be completed successfully.
In all of these examples known systems experience the problem of a UE 1001 not being connected to an Access Network for a period of time whilst a new Access Network is found and connected to.
The failure to provide a seamless network connection is a serious problem for the user of the UE 1001 since it results in an unacceptable degradation in performance.
It is an object of the present invention to overcome the above described problem of a moving UE 1001 losing the service(s) it has when connected to a given access network.